1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus for coding moving images and an image pickup apparatus using the same.
2. Description of the Related Art
Digital video cameras are now in wide use. Moving images taken by the digital video camera are generally recorded in MPEG (Moving Picture Experts Group) format. In the digital video cameras using the recording format such as MPEG format, the images shot by them are quantized and then compressed and coded. Quantization is a processing that affects the image quality and the amount of codes. If a quantization step is increased, the amount of codes can be reduced but the image quality will drop. Conversely, if the quantization step is reduced, the recording can be done in high quality but the amount of codes will increase.
The quantization step is generally determined based on the buffer occupancy (buffer fullness) and the amount of codes in each macroblock.
However, when the quantization step is simply determined based on the buffer occupancy and the like, there are cases where the amount of codes in a region of interest to a viewer is reduced and, conversely, an unduly large amount of codes is allocated to such a region as one having a large variation in which a subjective image quality may not be very improved even when the image is converted into a high quality image.